A You seem to want to leave primary teaching just as there is a push to encourage the Government to introduce language teaching into the primary sector.
As far as your qualification is concerned, you don't say what it is but I assume it is a PGCE covering the primary age range. Although there are elements of that course that would be useful, it will probably not have covered working with adult learners. At present a qualification isn't mandatory for teaching in further education.
There is certainly language teaching in FE, not least in sixth form colleges. You could try sending your cv to some FE colleges, but be aware that many posts are part-time and can involve evening work. Also, you may not be as well paid as you are in teaching.
Q I am 49 years old and wish to change my career course towards teaching. I have a maths degree and will complete a master's degree in science in September, both f which I studied for part-time while working. Can I train in parallel with my work as I did for my two degrees? Will my 22 days of holiday be enough for block practices in schools?
A You don't say why you want a change of career at this point. Have you heard about the shortage of maths and science teachers and want to help out?
Basically you have two options, either training on a part-time or modular PGCE course or through the graduate training programme employment-based route. The former will probably take at least two years and will require some time spent in schools demonstrating that you have mastered the skills required to obtain qualified teacher status. Then you will have to find a teaching post, but presumably you can retain your present employment while you look.
The graduate programme requires a school to offer you a training post and a salary of probably around pound;10-12,000. At the end of the training period you will have been paid for the year and acquired qualified teacher status but there will be no guarantee that the school will offer you a further contract; much will depend upon how well you do during the training period.
Both routes provide an entry into teaching, but neither is risk-free.